Expansible rotary drill bit

ABSTRACT

A rotary drill bit having cutters expanded outwardly to drill a hole substantially greater in diameter than the maximum effective diameter of the bit with its cutters fully retracted. The cutters are mounted on expandable and retractable supporting members spaced circumferentially around the bit, each supporting member having a cluster of cutters mounted thereon, the cutters in each cluster being circumferentially or radially spaced from each other, the cutters collectively cutting upon a formation shoulder in non-tracking relation. The tool is locked hydraulically with its cutters in a retracted position, and is unlocked to permit expansion of the cutters by fluid pressure. Air circulated down the outside of the tool aerates a liquid column within the tool and in the drill pipe connected to the tool, causing the greater hydrostatic head of fluid externally of the bit and drill pipe to flow across the bottom of the hole toward its axis to flush the hole bottom of cuttings, clean and cool the cutters, and carry the cuttings through the tool and drill pipe to a suitable discharge point above the top of the hole.

United States Patent Kammerer, Jr. et al.

[54] EXPANSIBLE ROTARY DRILL BIT [72] Inventors: Archer W. Kammerer, Jr., Fullerton; Gary R. Johnson, Anaheim, both of Calif.

[73] Assignee: Baker Oil Tools, Inc., City of Commerce, Calif.

[22] Filed: Nov. 16,1970

21 Appl. No.: 89,606

[52] U.S. Cl. ..175/267, 175/286, 175/376 [51] 1nt.Cl ..F2lb9/26 [58] Field of Search ..175/263-292, 391, 175/376 [56] References Cited UNITED STATES PATENTS 3,232,670 2/1966 Robbins etal ..175/267 2,725,222 11/1955 Robbins etal ..175/272 3,406,769 10/1968 Kammerer, Jr ..175/269 1,879,490 9/1932 Reamy et al ..175/278 3,215,214 1l/1965 Caro ..175/272 Primary Examiner-James A. Leppink Att0rneyl(endrick, Subkow & Kriegel 57 ABSTRACT A rotary drill bit having cutters expanded outwardly to drill a hole substantially greater in. diameter than the maximum effective diameter of the bit with its cutters fully retracted. The cutters are mounted on expandable and retractable supporting members spaced C11" cumferentially around the bit, each supporting member having a cluster of cutters mounted thereon, the cutters in each cluster being circumferentially or radially spaced from each other, the cutters collectively cutting upon a formation shoulder in non-tracking relation. The tool is locked hydraulically with its cutters in a retracted position, and is unlocked to permit expansion of the cutters by fluid pressure. Air circulated down the outside of the tool aerates a liquid column within the tool and in the drill pipe connected to the tool, causing the greater hydrostatic head of fluid externally of the bit and drill pipe to flow across the bottom of the hole toward its axis to flush the hole bottom of cuttings, clean and cool the cutters, and carry the cuttings through the tool and drill pipe to a suitable discharge point above the top of the hole.

29 Claims, 8 Drawing Figures EXPANSIBLE ROTARY DRILL BIT The present invention relates to rotary drill bits, and more particularly to rotary drill bits having expansible cutters for enlarging the diameters of bore holes.

Rotary drill bits having expansible cutters are used for passing through a bore hole casing, or into an open bore hole of a particular diameter, and of substantially enlarging the bore hole to another desired diameter. Difficulties have heretofore been encountered in providing expansible drill bits which are capable of enlarging holes of relatively large diameter to still substantially greater diameters. A multiplicity of rotary cutters has been used for performing a drilling action upon a transverse formation shoulder, or annular step, between the wall of the original hole and the wall of the enlarged hole, each cutter being mounted upon an individual supporting arm or member pivotally carried by the main body of the bit for outward movement from retracted to expanded positions to correspondingly shift the cutter carried thereby outwardly. The number of cutters and supporting arms or members could be reduced through use of larger diameter cutters. However, there is an optimum size that can be used, which, for example, may be about to 11 inches in diameter, cutters larger than such size becoming inefficient and, therefore, uneconomical. Because of the many cutters required to effectively cover the formation shoulder of relatively large area and radial extent, a correspondingly great multiplicity of cutter supporting members were required, which limited the number of arms and cutters that could be carried by the body structure for movement between retracted and expanded positions so that the cutters would be operable on the same formation shoulder. This limitation necessitated the provision of sets of arms and cutters longitudinally spaced from each other, the sets of cutters being expanded outwardly to progressively increased extents in upward sequence to enlarge the bore hole in stages or steps to the required final diameter. Accordingly, the prior expansible rotary drill hits were of extended length, possessed of a large number of parts, and comparatively complex and costly.

By virtue of the present invention, a rotary drill bit of the expansible type is provided, which is capable of en larging a comparatively large diameter hole, for example, about 5 feet in diameter, to a substantially greater diameter, for example,.about 8 feet, a relatively small number of cutter supporting members being used, all disposed in substantially the same transverse plane of operation, each supporting member carrying a multiplicity or cluster of cutters for collective operation upon substantially the entire area of the formation shoulder. The clustered cutters are preferably mounted in such manner as to be in non-tracking relation with respect to each other upon the formation shoulder. The rotary drill bit provided is of much shorter length than prior devices, embodying fewer parts. It is easier to as semble and dismantle and is more economical to manufacture. Each cutter and each cluster of cutters is replaceable, when worn, in a relatively simple and expeditious manner.

The supporting members and cutters of the expansible rotary drill bit are prevented from being expanded outwardly of the main body of the bit by a hydraulic lock, which is released when desired. Expansion of the supporting members and cutters occurs through use of compressed air, or other gaseous medium, as a motivating fluid, the compressed air also being used for effecting elevation of the cuttings produced by the cutters through the tool and drill pipe connected thereto to a desired disposal area.

This invention possesses many other advantages, and

has other purposes which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the-present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense.

Referring to the drawings:

FIG. 1 is a side elevational view, parts being shown in section, of a rotary drill bit embodying the invention disposed in a subaqueous bore hole, the cutters and the supporting members in which they are mounted being disposed in retracted position;

FIG. 2 is a partial longitudinal section, on an enlarged scale, through the drill bit illustrated in FIG. 1;

FIG. 3 is an enlarged section taken along the line 3 Son FIG. 1;

FIG. 4 is an enlarged section taken along the line 4 4 on FIG. 1;

FIG. 5 is a side elevational view of the drill bit, with its cutter supporting members and cutters in expanded position for enlarging the diameter of the bore hole;

FIG. 6 is an enlarged fragmentary section of a portion of the apparatus disclosed in FIG. 5;

FIG. 7 is a cross-section taken along the line 7--7 on FIG. 5;

FIG. 8 is an enlarged bottom plan view of a cluster of cutters mounted on the lower end of a supporting member.

A rotary expansible drill bit A is secured to the lower end of a rotary drill pipe string B extending upwardly to a drilling rig (not shown). As specifically illustrated, the drill bit is lowered through a bore hole C drilled downwardly from an ocean or sea floor D, the drill bit being of the expansible type so as to enlarge the diameter of the bore hole C. The rotary drill bit is particularly designed for enlarging bore holes of relatively large diameters.

The upper portion of the rotary drill bit consists of a tubular mandrel 10 that includes an upper kelly section 11 provided with an external flange 13 suitably bolted to a companion flange 14 at the lower end of a tubular adapter structure 15, the upper end of this structure having a flange 16 adapted to be bolted, or otherwise suitably secured, to the lower end 17 of the rotary drill pipe string B that extends upwardly through the water to the drilling rig used for rotating the apparatus and for imposing appropriate drilling weight thereon. The lower portion 18 of the kelly or upper mandrel section 11 is slidably splined to a body structure 19 of the drill bit, by making such lower portion of the kelly non-circular in external shape, which fits within a companion non-circular bore 20 of a companion section 21 of the body structure, the mandrel 10 and body structure 19 being longitudinally shiftable with respect to each other, with rotary motion and torque being transmittable from the kelly to the body structure.

The body structure includes an upper cylinder portion 22 that has a lower cylinder head 23 at the upper end of the torque drive section 21 of the body structure, and into which the kelly 1 1 is slidably splined. The lower head 23 of the cylinder is secured to a cylinder skirt 24 in any suitable manner, as by means of screws 25, a gasket between the lower end of the sleeve and head preventing leakage therebetween. The upper end of the cylinder sleeve is suitably secured, as by the use of welding material 26, to an upper head 27 that extends inwardly to the cylindrical portion 28 of the kelly section. Leakage of fluid between the upper head and kelly is prevented by a suitable side seal ring 29 in the upper head slidably and sealingly engaging the kelly periphery 28. Similarly, leakage of fluid between the lower head 23 and cylindrical perimeter 28 of the kelly is prevented by one or more side seal rings 30 in the head slidably and sealingly engaging against the kelly.

The sleeve 24 is laterally spaced from the periphery 28 of the kelly to define an annular cylinder space 31 therebetween, which is divided by a piston 32 secured to the kelly into an upper pressure expander chamber 33 and a lower lock chamber 34. The piston is secured to the kelly by longitudinally spaced snap rings 35 disposed in kelly grooves 36 and engaging upwardly facing and downwardly facing surfaces of the piston 32, fluid leakage between the piston and kelly being prevented by a suitable side seal ring 37 in the kelly engaging the inner periphery of the piston. Similarly, leakage of fluid between the exterior of the piston and the cylinder sleeve 24 is prevented by a suitable piston or seal ring 38 on the piston slidably and sealingly engaging the inner wall of the cylinder skirt.

The mandrel includes a lower section 39, which is swivelly connected to the kelly section 11 thereabove by means of a split ring 40 received within a peripheral groove 41 in the lower mandrel section and which underlies and engages a downwardly facing kelly shoulder 42. A split ring 43 is received within an inner circumferential groove 44 in the kelly which underlies the other ring 40, the kelly ring being retained in its groove and in underlying relation to the other ring by a sleeve 45 encircling the lower member 39 and disposed behind the kelly ring 43, downward movement of this sleeve being prevented by one or a plurality of screws 46 threaded into the lower mandrel section 39 and underlying the retainer ring 45. The lower mandrel section 39 extends into a cutter supporting body section 47 which is suitably secured, as by means of bolts or screws 48, to the torque drive body section 21, the lower end of the lower mandrel section being telescopically arranged within a lower body section 49 suitably secured to the cutter supporting section 47 by one or a plurality of bolts or screws 50. This lower section has a bottom flange 51 to which the upper flange 52 of a suitable rotary drill bit E can be secured by bolts 53, or the like, the lower body section having a central passage 54 therethrough communicating with a central passage 55 in the lower drill bit which opens into the bore hole C therebelow. The body of the lower drill bit E has a plurality of cutters 56 thereon to cover the entire bottom area of the bore hole to drill the same. The disposition of the cutters 56 on the lower drill bit forms no part of the present invention, and for that reason is not illustrated. A very large number of the cutters 56 secured to the body of the lower drill bit are not illustrated in the interest of clarity. It is suffic'ient to note that the lower drill bit will drill the bore hole C to an initial diameter, such as illustrated in FIG. 1 of the drawings.

The body structure has a plurality of expansible parts mounted on it, including cutter supporting members 57 spaced circumferentially around the body structure, each cutter supporting member being pivotally mounted in a body slot 58 on a hinge pin 59 secured to the cutter mounting body section 47. As shown, the sides of each slot are provided by vertically disposed parallel side plates 60 welded, or otherwise suitably secured, to the upper and lower flanges of the body sec tion 47, the cutter supporting member or arm 57 being slidable along such side plates so that torque can be transmitted from the body structure 19 to the cutter supporting member. Each supporting member or arm has stop elements 61 secured to its sides that are engageable with companion stop elements 62 on the vertical side plates, to limit the maximum extent of outward expansion of the supporting members.

Each cutter supporting member 57 terminates at its lower end in a mounting base 63 extending transversely beyond the sides of the supporting member thereabove. Secured to each mounting base, as by means of threaded studs 64, or the like, are a plurality of mounting heads 65 from which arms 66 depend having bearing supporting pins 67 extending inwardly thereof, on each of which a roller cutter 68a, 68b, 680 or 68d is rotatably mounted, in a known manner. As disclosed, a cluster of cutters 68a, 68b, 68c, 68d is carried by each supporting member 57, the cutters being individually rotatably about their supporting bearings 67, some of the cutters 68a, 68b and 68c, 68d being radially spaced from each other, some cutters, such as 68a, 68c and 68b, 68d also being circumferentially spaced from one another. The arrangement is such that a relatively large number of cutters can be carried by each supporting arm, and yet the supporting arms 57 and their cutters can be substantially fully nested within the confines of the body structure 19 when in a retracted position. When expanded outwardly, the sets of cutters will collectively operate upon the entire annular formation shoulder S that will be produced in the bore hole as a' result of outward expansion and rotation of the supporting members and cutters, the cutters in each set being differently arranged on each supporting arm so that the cutters do not track one another upon the formation shoulder. As shown, the cutters 68a, 68b of each set rotate about axes lying in a radial plane through the bit axis angularly displaced with respect to the radial plane in which the rotational axes of the cutters 68c, 68d lie. Moreover, the radial spacing between the cutters 68a, 68b is substantially smaller than the radial spacing between the cutters 68c, 68d. The cutters extend different radial distances from the bit axis to assure coverage of the full shoulder S by the cutters. With a minimum number of supporting members and by virtue of the use of a cluster of cutters carried by each supporting member, a large increase in bore hole diameter can be secured with respect to a large diameter initial bore hole C using a limited number of cutter supporting members 57, which all operate substantially in substantially the same plane.

The cutter supporting members 57 and cutter 68a-68 carried thereby tend to occupy a retracted position substantially entirely within the confines of the body structure 19 of the expansible bit. These cutter supporting members and cutters are expandable outwardly to enlarge the diameter of the well bore H and to operate upon the formation shoulder S that the cutters produce in the latter as a result of their outward expansion. To accomplish the expansion, each cutter supporting member 57 has an inclined expander surface 70 on its inner portion below the hinge pin 59 which tapers in a downward and inward direction. Each expander surface terminates in a lock surface 71 formed on the cutter supporting member. The outward expansion is accomplished by producing relative longitudinal movement between the mandrel and the body structure 19, which will produce corresponding relative longitudinal movement between the cutter supporting members 57 and lock and expander sections 72 formed on the lower mandrel section 39 projecting outwardly into the mandrel slots 58. The lock and expander portions are adapted to engage the expander surfaces 70 and the lock surfaces 71. Upon relative downward movement of the lock and expander portions 72 along the cutter supporting members, they engage and slide downwardly along the expander surfaces 70, shifting the supporting members 57 and cutters 68-68d outwardly while the expansible rotary drill bit A is being rotated by the string of drill pipe B, the outermost cutters 68a digging into the formation wall to effect an enlargement of the hole diameter. Outward expansion continues until the lower end 11a of the kelly 11 bottoms against a wear plate 75 clamped between the lower and upper ends of the torque and cutter mount ing body sections 21, 47, at which time lock surfaces 76 on the members 72 will be disposed behind their companion lock surfaces 71 on the supporting members 57, further outward expansion of the supporting members being prevented by engagement of their stop shoulders 61 with companion shoulders 62 on the vertical plates 60 of the body section 47.

Relative longitudinal movement between the mandrel 10 and body structure 19 is initially prevented by disposing the mandrel in its uppermost position with respect to the body structure, the piston 32 engaging the upper cylinder head 27, and the lock chamber 34 being filled with sea water, or other liquid, retained therein, but which can be permitted to bleed therefrom by opening a suitable valve 80 secured to the-lower head and which communicates with the lock chamber. Assuming that the liquid in the lock chamber 34 has been permitted to bleed therefrom, a suitable fluid medium, such as compressed air, or other compressed gas, is forced through a compressed air line 81 extending downwardly from the drilling rig and along the drill pipe B, this air line communicating with a pipe 82 connected to the upper head 27 and which communicates with the pressure expansion chamber 33. Air under pressure will enter the expansion chamber, acting upon the upper cylinder head 27 and elevating the body structure 19 along the mandrel 10 while the drill pipe B and body structure are rotated, the rotation of the body structure being transferred through the plates 60 to the cutter supporting members 57 to rotate the latter and their cutters 68a-68d in the bore hole, to effect cutter expansion and the production of the formation shoulder S, as described above. Once the cutter supporting members and cutters have been expanded outwardly to their maximum extent, drilling weight is transmitted through the string of drill pipe B to the mandrel 10, from the lower end 11a of the mandrel kelly to the body structure, this drilling weight passing through the stop shoulders 62, 61 to the cutter supporting members 57 and cutters 68a-68d which are bearing upon the formation shoulder S while the apparatus is being rotated by the drill string.

The cuttings produced by the cutters are circulated from the bore hole by compressed air pumped down the same line 81 that conducts air to the pressure chamber 33, as well as through one or more other com pressed air lines 81a extending downwardly along the drill pipe. Thus, a compressed air line 83 extends from the branch 82 leading to the pressure chamber, this line extending downwardly along the body structure and communicating with a radial air inlet port 84 in the lower body section below the expansible cutters, the air discharging therefrom through orifices 85 into the central passage 54 in the lower body section 49, which communicates with the tubular mandrel 1'0 and the rotary drill pipe B thereabove. Similarly, the other compressed air line 81a extends downwardly along the apparatus and communicates with an :air inlet port 84 that opens through orifices 85 into the central passage 54. The pumping of air through the lines into the central passage will aerate or lighten the liquid column in thecentral passage through the apparatus A and in the rotary drill pipe string B, causing the water in the well bore, such as the ocean water, surrounding the ap paratus and the drill pipe to flow downwardly around the exterior of the apparatus to the lower drill bit E, and then upwardly through the central passages 55, 54, flushing the cuttings in the bore hole produced by the expandable cutters 68a68d toward the axis, of the apparatus, and then conveying them upwardly at a substantial velocity through the central passages 55, 54, mandrel 10 and the string of drill pipe B to the drilling rig for suitable disposal.

The bleeder valve is disclosed only diagrammatically since its specific details from no part of the present invention. It is sufficient to state that such valve is remotely controlled from the drilling rig, being closed when the cutters and supporting members 57 are in retracted position with the lock chamber 34 filled with sea water or other liquid. All of the compressed air pumped down through the air lines 81, 81a discharge into the central passage 54 to aerate and thus lighten the fluid column in the bit A, as well as in the drill pipe B, so that the cuttings in the well bore can be flushed upwardly through the bit and drill pipe.

With the apparatus disclosed, the expansible drill bit portion A is retained locked in its retracted condition and the initial diameter of bore hole C can be drilled commencing from the ocean floor D by the lower drill bit E, while compressed air is being pumped down through the lines 81, 81a, the cuttings being carried upwardly through the central passages 55, 54, mandrel 10 and drill pipe B. When the hole has been drilled to the desired depth, the apparatus can be elevated to a location at which enlargement of the bore hole is to com-1 mence, whereupon the bleeder valve 80 is opened to allow discharge of the locking liquid from the lock chamber 34, compressed air entering the upper pressure chamber 33 to elevate the body structure 19 with respect to the mandrel while the rotary drill string B and body structure are rotated, the expander surfaces 70 on the cutter supporting members 57 engaging the lock and expander 72 and being gradually expanded outwardly while the rotation of the apparatus continues, so that the cutters 68a enlarge the hole to a greater diameter H, the extent of enlargement being determined by engagement of the stop shoulders 61 on the supporting members with the companion stop shoulder 62 of the body structure, at which time the lock portions 76 of the lock and expander members are disposed behind the lock surfaces 71 to prevent the supporting members and cutters from being moved inwardly. When the well bore H has been enlarged to the required diameter, as determined by the extent of outward expansion of the supporting members and cutters, downward drilling weight is imposed on the drill pipe B and mandrel 10 which is transmitted to the body structure 19, cutter supporting members 57 and cutters 68a, 68d, the drill pipe being rotated to rotate the apparatus. At the same time, compressed air is flowing through the lines 81, 81a, 83 and discharging into the central passage 54, aerating the liquid column therein and in the drill pipe so that the sea water flushes the cuttings produced to the lower end of the passage 55 and upwardly therethrough for conveyance to the drilling rig, or other suitable location above the ocean floor. The hole enlarging operation continues until the well bore H has been enlarged downwardly to the desired longitudinal extent.

The apparatus can now be retracted by ceasing pumping of air through the line 81 and elevating the string of drill pipe B, which will pull the mandrel 10 upwardly to dispose the lock and expander elements 72 above the expander surfaces 70, these lock elements engaging fingers 90 on the supporting members 57 extending inwardly from the pivot pins 59, so as to swing such fingers inwardly and the supporting arms and cutters below the hinge pins inwardly to their fully.

retracted position. The apparatus can now be elevated and removed from the bore hole.

Inthe event that any of the cutters 68a-68 d becomes worn, such cutter is readily replaced by removing the head 65 from the mounting base 63 of the supporting arm through removal of the studs 64, a new cutter and head assembly being substituted in its place and secured to the mounting base.

In the event that the initial bore hole C has previously been drilled, the lower drill bit E need not be used at all, the apparatus A being lowered by the drill pipe B into the bore hole to the location at which the hole enlarging operation is to commence, after which the supporting members 57 and cutters 68a-68d are expanded outwardly and the hole enlarged to the desired extent, in the manner described above, the supporting members and cutters being retracted by picking up on the mandrel 10, the lock and expanders 72 engaging the fingers 90 to swing the supporting members and cutters inwardly.

We claim:

1. In a rotary drill bit to be lowered in a bore hole: a main body; means for rotating said body; circumferentially spaced supporting members mounted on said body for expansion laterally outwardly of said body and for rotation with said body; a plurality of roller cutters carried by each supporting member for enlarging the diameter of the bore hole and thereby produce a transverse shoulder therein and for operation upon the transverse formation shoulder; some of the cutters carried by each supporting member being circumferentially spaced from each other, some of the cutters carried by each supporting member being laterally spaced from each other; and means operable while said main body, supporting members and cutters are being rotated by said rotating means for expanding said supporting members and cutters carried thereby laterally outwardly of said body for enlarging the bore hole diameter and for operation of said cutters upon the transverse formation shoulder.

2. In a rotary drill bit as defined in claim 1; said cutters laterally spaced from each other being rotatable about axes lying in a plane radial of the longitudinal axis of said body.

3. In a rotary drill bit as defined in claim 1; one of said cutters carried by each supporting member extending laterally outwardly beyond said supporting member for engagement with the wall of the bore hole to enlarge the bore hole and cut the transverse shoulder therein upon lateral outward expansion of said supporting members and cutters.

4. In a rotary drill bit as defined in claim 1; and detachable means mounting each roller cutter individually on the lower end of its supporting member.

5. In a rotary drill bit as defined in claim 1; said cutters longitudinally spaced from each other being rotatable about axes lying in a plane radial of the longitudinal axis of said body; one of said cutters carried by each supporting member extending laterally outwardly beyond said supporting member for engagement with the wall of the bore hole to cut the transverse shoulder therein upon lateral outward expansion of said supporting members and cutters.

6. In a rotary drill bit as defined in claim 1; said cutters laterally spaced from each other being rotatable about axes lying in a plane radial of the longitudinal axis of said body; one of said cutters carried by each supporting member extending laterally outwardly beyond said supporting member for engagement with the wall of the bore hole to enlarge the bore hole and cut the transverse shoulder therein upon lateral outward expansion of said supporting members and cutters; and detachable means mounting each roller cutter individually on the lower end of its supporting member.

7. In a rotary drill bit as defined in claim 1; a first plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a first plane radial of the longitudinal axis of said body; a second plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a second plane radial of the longitudinal axis of said body; said first and second planes being arcuately displaced from each other.

8. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members mounted on said body for expansion laterally outwardly of said body; a plurality of roller cutters carried by each supporting member for operation upon a transverse formation shoulder in the bore hole; some of the cutters carried by each supporting member being circumferentially spaced from each other, some of the cutters carried by each supporting member being laterally spaced from each other; and means for expanding said supporting members and cutters carried thereby laterally outwardly of said body for operation of said cutters upon the transverse formation shoulder; a first plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a first plane radial of the longitudinal axis of said body; a second plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about V axes lying in a second plane radial of the longitudinal axis of said body; said first and second planes being arcuately displaced from each other, the lateral spacing between said vfirst plurality of cutters being substantially greater than the lateral spacing between said second plurality of cutters.

9. In a rotary drill bit to be lowered in a bore hole: a main body; means for rotating said body; circumferentially spaced supporting members pivotally mounted at their upper portions on said body for expansion laterally outwardly of said body and for rotation with said body; each supporting member having a lower mounting base portion extending transversely in opposite directions substantially beyond the sides of the portion of the supporting member thereabove; a plurality of roller cutters for each supporting member for enlarging the diameter of the bore hole and thereby produce a transverse shoulder therein and for operation upon the transverse formation shoulder; a head for each cutter; means secured to each head rotatably mounting a cutter; and means for securing each head to the bottom of said base portion with its roller cutter below said base portion; said heads and cutters being so carried by said base portion that some of the cutters are circumferentially spaced from each other, some of the cutters being laterally spaced from each other; and means operable while said main body, supporting members and cutters are being rotated by said rotating means for expanding said supporting members and cutters laterally outwardly of said body for enlarging the bore hole diameter and for operation of said cutters upon the transverse formation shoulder in the bore hole.

10. In a rotary drill bit as defined in claim 9; a first plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a first plane radial of the longitudinal axis of said body; a second plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a second plane radial of the longitudinal axis of said body; said first and second planes being arcuately displaced from each other.

11. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members pivotally mounted at their upper portions on said body for expansion laterally outwardly of said body; each supporting member having a lower mounting base portion extending transversely in opposite directions substantially beyond the sides of the portion of the supporting member thereabove; a plurality of roller cutters for each supporting member; a head for each cutter; means secured to each head rotatably mounting a cutter; and means for securing each head to the bottom of said base portion with its roller cutter below said base portion; said heads and cutters being so carried by said base portion that some of the cutters are circumferentially spaced from each other, some of the cutters being laterally spaced from each other; and means for expanding said supporting members and cutters laterally outwardly of said body for operation of said cutters upon a transverse formation shoulder in the bore hole; a first plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in 'a first plane radial of the longitudinal axis of said body; a second plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a second plane radial of the longitudinal axis of said body; said first and second planes being arcuately displaced from each other; the lateral spacing between said first plurality of cutters being substantially greater than the lateral spacing between said second plurality of cutters.

12. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting membersmounted on said body for expansion laterally outwardly of said body; a plurality of roller cutters carried by each supporting member for operation upon a transverse formation shoulder in the bore hole; some of the cutters carried by each supporting member being circumferentially spaced from each other, some of the cutters carried by each supporting member being laterally spaced from each other; a mandrel connectible to a drill string and slidably :splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and supporting members; and means for relatively shifting said body, supporting members and roller cutters longitudinally with respect to said mandrel while said mandrel and body are rotated by the drill string to cause said expander means to expand said supporting members and cutters laterally outwardly of said body for some of said cutters to enlarge the diameter of the bore holeand for said cutters to operate upon the transverse formationshoulder.

13. In a rotary drill bit as defined in claim 12; a first plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a first plane radial of the longitudinal axis of said body; a second plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a second plane radial of the longitudinal axis of said body; said first and second planes being arcuately displaced from each other.

14. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members mounted on said body for expansion laterally outwardly of said body; a plurality of roller cutters carried by each supporting member for operation upon a transverse formation shoulder in the bore hole; some of the cutters carried by each supporting member being circumferentially spaced from each other, some of the cutters carried by each supporting member being laterally spaced from each other; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and supporting members; and means for relatively shifting said body, supporting members and roller cutters longitudinally with respect to said mandrel to cause said expander means to expand said supporting members and cutters laterally outwardly of said body for operation of said cutters upon the transverse formation shoulder; a first plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a first plane radial of the longitudinal axis of said body; a second plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a second plane radial of the longitudinal axis of said body; said first and second planes being arcuately displaced from each other; the lateral spacing between said first plurality of cutters being substantially greater than the lateral spacing between said second plurality of cutters.

15, In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members pivotally mounted at their upper portions on said body for expansion laterally outwardly of said body; each supporting member having a lower mounting base portion extending circumferentially in opposite directions substantially beyond the sides of the portion of the supporting member thereabove; a plurality of roller cutters for each supporting member; a head for each cutter; means secured to each head rotatably mounting a cutter; means for securing each head to the bottom of said base portion with its roller cutter below said base portion; said heads and cutters being so carried by said base portion that some of the cutters are circumferentially spaced from each other, some of the cutters being laterally spaced from each other; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and supporting member; and means for relatively shifting said body, supporting members and roller cutters longitudinally with respect to said mandrel while said mandrel and body are rotated by the drill string to cause said expander means to expand said supporting members and cutters laterally outwardly of said body for some of said cutters to enlarge the diameter of the bore hole and for said cutters to operate upon a transverse formation shoulder in the bore hole.

16. In a rotary drill bit as defined in claim a first plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a first plane radial of the longitudinal axis of said body; a second plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a second plane radial of the longitudinal axis of said body; said first and second planes being arcuately displaced from each other.

17. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members pivotally mounted at their upper portions on said body for expansion laterally outwardly of said body;

each supporting member having a lower mounting base portion extending circumferentially in opposite directions substantially beyond the sides of the portion of the supporting member thereabove; a plurality of roller cutters for each supporting member; a head for each cutter; means secured to each head rotatably mounting a cutter; means for securing each head to the bottom of said base portion with its roller cutter below said base portion; said heads and cutters being so carried by said base portion that some of the cutters are circumferentially spaced from each other, some of the cutters being laterally spaced from each other; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and supporting member; and means for relatively shifting said body, supporting members and roller cutters longitudinally with respect to said mandrel to cause said expander means to expand said supporting members and cutters laterally outwardly of said body for operation of said cutters upon a transverse formation shoulder in the bore hole; a first plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a first plane radial of the longitudinal axis of said body; a second plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a second plane radial of the longitudinal axis of said body; said first and second planes being arcuately displaced from each other; the lateral spacing between said first plurality of cutters being substantially greater than the lateral spacing between said second plurality of cutters.

18. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members mounted on said body for expansion laterally outwardly of said body; a plurality of roller cutters carried by each supporting member for operation upon a transverse shoulder in the bore hole; some of the cutters carried by each supporting member being circumferentially spaced from each other, some of the cutters carried by each supporting member being laterally spaced from each other; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and supporting members; said body having a cylinder portion above said expander means slidably and sealingly engaging said mandrel; said mandrel having a piston portion in said cylinder portion slidably and sealingly engaging said cylinder portion and dividing said cylinder portion into upper and lower fluid pressure chambers; and means for feeding fluid under pressure into one of said chambers to relatively shift said body, supporting members and roller cutters longitudinally with respect to said mandrel while said mandrel and body are rotated by the drill string to cause said expander means to expand said supporting members and cutters laterally outwardly of said body for some of said cutters to enlarge the diameter of the bore hole and for said cutters to operate upon the transverse formation shoulder.

19. In a rotary drill bit as defined in claim 18; said fluid feeding means comprising a conduit externally of said mandrel communicating with said one of said chambers.

20. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members mounted on said body for expansion laterally outwardly of said body; a plurality of roller cutters carried by each supporting member for operation upon a transverse shoulder in the bore hole; some of the cutters carried by each supporting member being circumferentially spaced from each other, some of the cutters carried by each supporting member being laterally spaced from each other; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and supporting members; said body having a cylinder portion above said expander means slidably and sealingly engaging said mandrel; said mandrel having a piston portion in said cylinder portion slidably and sealingly engaging said cylinder portion and dividing said cylinder portion into upper and lower fluid pressure chambers; and means for feeding fluid under pressure into one of said chambers to relatively shift said body, supporting members and roller cutters longitudinally with respect to said mandrel to cause said expander means to expand said supporting members and cutters laterally outwardly of said body for operation of said cutters upon the transverse formation shoulder; a liquid confined in said other of said chambers initially preventing such relative longitudinal shifting; and means for releasing said liquid from said other of said chambers while the drill bit is in the bore hole.

21. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members mounted on said body for expansion laterally outwardly of said body; a plurality of roller cutters carried by each supporting member for operation upon a transverse shoulder in the bore hole; some of the cutters carried by each supporting member being circumferentially spaced from each other, some of the cutters carried by each supporting member being laterally spaced from each other; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and supporting members; said body having a cylinder portion above said expander means slidably and sealingly engaging said mandrel; said mandrel having a piston portion in said cylinder portion slidably and sealingly engaging said cylinder portion and dividing said cylinder portion into upper and lower fluid pressure chambers; and means for feeding fluid under pressure into one of said chambers to relatively shift said body, supporting members and roller cutters longitudinally with respect to said mandrel to cause said expander means to expand said supporting members and cutters laterally outwardly of said body for operation of said cutters upon the transverse formation shoulder; said one of said chambers being said upper chamber whereby fluid under pressure fed thereinto elevates said body, supporting members and cutters along said mandrel.

22. In a rotary drill bit as defined in claim 21; a liquid confined in said lower chamber initially preventing elevation of said body, supporting members and cutters along said mandrel; and means for releasing said liquid from said lower chamber while the drill bit is in the bore hole.

23'. In a rotary drill bit as defined in claim 21; a liquid confined in said lower chamber initially preventing elevation of said body, supporting members and cutters along said mandrel; and means for releasing said liquid from said lower chamber while the drill bit is in the bore hole; said fluid feeding means comprising a conduit externally of said mandrel communicating with said upper chamber.

24. In a rotary drill bit as defined in claim 21; a liquid confined in said lower chamber initially preventing elevation of said body, supporting members and cutters along said mandrel; and means for releasing said liquid from said lower chamber while the drill bit is in the bore hole; said fluid feeding means comprising a conduit externally of said mandrel communicating with said upper chamber; and means for feeding compressed air into said mandrel to aerate the liquid column therein and in the drill string thereabove, whereby liquid in the well'bore externally of the drill bit flushes cuttings into the mandrel for upward passage through the mandrel and drill string.

25. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members mounted on said body for expansion laterally outwardly of said body; a plurality of roller cutters carried by each supporting member for operation upon a transverse formation shoulder in the bore hole; some of the cutters cam'ed by each supporting member being circumferentially spaced from each other, some of the cutters carried by each supporting member being laterally spaced from each other; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and supporting members; and means for relatively shifting said body, supporting members and roller cutters longitudinally with respect to said mandrel to cause said expander means to expand saidsupporting members and cutters laterally outwardly of said body for operation of said cutters upon the transverse formation shoulder; and means for feeding compressed air into said mandrel to aerate the liquid column therein and in the drill string thereabove, whereby liquid in the well bore externally of the drill bit flushes cuttings into the mandrel for upward passage through the mandrel and drill string.

26. In a rotary drill bit to be lowered in a bore hole: a main body; cutter means mounted on said body for expansion laterally outwardly of said body; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and cutter means; said body having a cylinder portion above said expander means slidably and sealingly engaging said mandrel; said mandrel having a piston portion in said cylinder portion slidably and sealingly engaging said cylinder portion and dividing said cylinder portion into upper and lower fluid pressure chambers; means for feeding fluid under pressure into one of said chambers to relatively shift said body and cutter means longitudinally with respect to said mandrel to cause said expander means to expand said cutter means laterally outwardly of said body; a liquid confined in said other of said chambers initially preventing such relative longitudinal shifting; and means for releasing said liquid from said other of said chambers while the drill bit is in the bore hole.

27. In a rotary drill bit as defined in claim 26; said one of said chambers being said upper chamber, whereby fluid under pressure fed thereinto elevates said body and cutter means along said mandrel; said other of said chamber being said lower chamber in which the liquid is confined.

28. In a rotary drill bit as defined in claim 26; said one of said chambers being said upper chamber, whereby fluid under pressure fed thereinto elevates said body and cutter means along said mandrel; said other of said chamber being said lower chamber in which the liquid is confined; said fluid feeding means comprising a conduit externally of said mandrel communicating with said upper chamber.

29. In a rotary drill bit as defined in claim 26; said one of said chambers being said upper chamber, whereby fluid under pressure fed thereinto elevates said body and cutter means along said mandrel; said other of said chamber being said lower chamber in which the liquid is confined; said fluid feeding means comprising a conduit externally of said mandrel communicating with said upper chamber; and means for feeding compressed air into said mandrel to aerate the liquid column therein and in the drill string thereabove, whereby liquid in the well bore externally of the drill bit through the mandrel and drill string.

23 2 3 UNl'lED STATES PATENT. OFFICE I CER'JQH ICATE OF (IQRREC'IION Patent No. 3 .684 ,041 Deted August 15 197.2 I lnmlwfls) ARCHER KAMMERER, JR. ET AL It is certified that error appears in the above-identified parent and that said Letters Patent are hereby corrected as shown below:

I o x y ","I Column 5, "line 2, change "68" to ----68d--.

line 28, change "68" to --68a--.

Column 8, line 33 (claim 5, line 2), cancel "longitudinally" and substitute --lateral ly--. line 38 (claim 5, line 7),.after "to" insert --enlarge the bore hole and--.

Signed and sealed this 6th day of March 1973 (SEAL) Attest:

EDWARD M.FLETCHER,JR. I ROBERT GOTTSCHALK Attes'ting' Officer Commissioner of Patents 

1. In a rotary drill bit to be lowered in a bore hole: a main body; means for rotating said body; circumferentially spaced supporting members mounted on said body for expansion laterally outwardly of said body and for rotation with said body; a plurality of roller cutters carried by each supporting member for enlarging the diameter of the bore hole and thereby produce a transverse shoulder therein and for operation upon the transverse formation shoulder; some of the cutters carried by each supporting member being circumferentially spaced from each other, some of the cutters carried by each supporting member being laterally spaced from each other; and means operable while said main body, supporting members and cutters are being rotated by said rotating means for expanding said supporting members and cutters carried thereby laterally outwardly of said body for enlarging the bore hole diameter and for operation of said cutters upon the transverse formation shoulder.
 2. In a rotary drill bit as defined in claim 1; said cutters laterally spaced from each other being rotatable about axes lying in a plane radial of the longitudinal axis of said body.
 3. In a rotary drill bit as defined in claim 1; one of said cutters carried by each supporting member extending laterally outwardly beyond said supporting member for engagement with the wall of the bore hole to enlarge the bore hole and cut the transverse shoulder therein upon lateral outward expansion of said supporting members and cutters.
 4. In a rotary drill bit as defined in claim 1; and detachable means mounting each roller cutter individually on the lower end of its supporting member.
 5. In a rotary drill bit as defined in claim 1; said cutters longitudinally spaced from each other being rotatable about axes lying in a plane radial of the longitudinal axis of said body; one of said cutters carried by each supporting member extending laterally outwardly beyond said supporting member for engagement with the wall of the bore hole to cut the transverse shoulder therein upon lateral outward expansion of said supporting members and cutters.
 6. In a rotary drill bit as defined in claim 1; said cutters laterally spaced from each other being rotatable about axes lying in a plane radial of the longitudinal axis of said body; one of said cutters carried by each supporting member extending laterally outwardly beyond said supporting member for engagement with the wall of the bore hole to enlarge the bore hole and cut the transverse shoulder therein upon lateral outward expansion of said supporting members and cutters; and detachable means mounting each roller cutter individually on the lower end of its supporting member.
 7. In a rotary drill bit as defined in claim 1; a first plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a first plane radial of the longitudinal axis of said body; a second plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a second plane radial of the longitudinal axis of said body; said first and second planes being arcuately displaced from each other.
 8. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members mounted on said body for expansion laterally outwardly of said body; a plurality of roller cutters carried by each supporting member for operation upon a transverse formation shoulder in the bore hole; some of the cutters carried by each supporting member being circumferentially spaced from each other, some of the cutters carried by each supporting member being laterally spaced from each other; and means for expanding said supporting members and cutters carried thereby laterally outwardly of said body for operation of said cutters upon the transverse formation shoulder; a first plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a first plane radial of the longitudinal axis of said body; a second plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a second plane radial of the longitudinal axis of said body; said first and second planes being arcuately displaced from each other, the lateral spacing between said first plurality of cutters being substantially greater than the lateral spacing between said second plurality of cutters.
 9. In a rotary drill bit to be lowered in a bore hole: a main body; means for rotating said body; circumferentially spaced supporting members pivotally mounted at their upper portions on said body for expansion laterally outwardly of said body and for rotation with said body; each supporting member having a lower mounting base portion extending transversely in opposite directions substantially beyond the sides of the portion of the supporting member thereabove; a plurality of roller cutters for each supporting member for enlarging the diameter of the bore hole and thereby produce a transverse shoulder therein and for operation upon the transverse formation shoulder; a head for each cutter; means secured to each head rotatably mounting a cutter; and means for securing each head to the bottom of said base portion with its roller cutter below said base portion; said heads and cutters being so carried by said base portion that some of the cutters are circumferentially spaced from each other, some of the cutters being laterally spaced from each other; and means operable while said main body, supporting members and cutters are being rotated by said rotating means for expanding said supporting members and cutters laterally outwardly of said body for enlarging the bore hole diameter and for operation of said cutters upon the transverse formation shoulder in the bore hole.
 10. In a rotary drill bit as defined in claim 9; a first plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a first plane radial of the longitudinal axis of said body; a second plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a second plane radial of the loNgitudinal axis of said body; said first and second planes being arcuately displaced from each other.
 11. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members pivotally mounted at their upper portions on said body for expansion laterally outwardly of said body; each supporting member having a lower mounting base portion extending transversely in opposite directions substantially beyond the sides of the portion of the supporting member thereabove; a plurality of roller cutters for each supporting member; a head for each cutter; means secured to each head rotatably mounting a cutter; and means for securing each head to the bottom of said base portion with its roller cutter below said base portion; said heads and cutters being so carried by said base portion that some of the cutters are circumferentially spaced from each other, some of the cutters being laterally spaced from each other; and means for expanding said supporting members and cutters laterally outwardly of said body for operation of said cutters upon a transverse formation shoulder in the bore hole; a first plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a first plane radial of the longitudinal axis of said body; a second plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a second plane radial of the longitudinal axis of said body; said first and second planes being arcuately displaced from each other; the lateral spacing between said first plurality of cutters being substantially greater than the lateral spacing between said second plurality of cutters.
 12. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members mounted on said body for expansion laterally outwardly of said body; a plurality of roller cutters carried by each supporting member for operation upon a transverse formation shoulder in the bore hole; some of the cutters carried by each supporting member being circumferentially spaced from each other, some of the cutters carried by each supporting member being laterally spaced from each other; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and supporting members; and means for relatively shifting said body, supporting members and roller cutters longitudinally with respect to said mandrel while said mandrel and body are rotated by the drill string to cause said expander means to expand said supporting members and cutters laterally outwardly of said body for some of said cutters to enlarge the diameter of the bore hole and for said cutters to operate upon the transverse formation shoulder.
 13. In a rotary drill bit as defined in claim 12; a first plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a first plane radial of the longitudinal axis of said body; a second plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a second plane radial of the longitudinal axis of said body; said first and second planes being arcuately displaced from each other.
 14. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members mounted on said body for expansion laterally outwardly of said body; a plurality of roller cutters carried by each supporting member for operation upon a transverse formation shoulder in the bore hole; some of the cutters carried by each supporting member being circumferentially spaced from each other, some of the cutters carried by each supporting member being laterally spaced from each other; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling toRque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and supporting members; and means for relatively shifting said body, supporting members and roller cutters longitudinally with respect to said mandrel to cause said expander means to expand said supporting members and cutters laterally outwardly of said body for operation of said cutters upon the transverse formation shoulder; a first plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a first plane radial of the longitudinal axis of said body; a second plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a second plane radial of the longitudinal axis of said body; said first and second planes being arcuately displaced from each other; the lateral spacing between said first plurality of cutters being substantially greater than the lateral spacing between said second plurality of cutters.
 15. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members pivotally mounted at their upper portions on said body for expansion laterally outwardly of said body; each supporting member having a lower mounting base portion extending circumferentially in opposite directions substantially beyond the sides of the portion of the supporting member thereabove; a plurality of roller cutters for each supporting member; a head for each cutter; means secured to each head rotatably mounting a cutter; means for securing each head to the bottom of said base portion with its roller cutter below said base portion; said heads and cutters being so carried by said base portion that some of the cutters are circumferentially spaced from each other, some of the cutters being laterally spaced from each other; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and supporting member; and means for relatively shifting said body, supporting members and roller cutters longitudinally with respect to said mandrel while said mandrel and body are rotated by the drill string to cause said expander means to expand said supporting members and cutters laterally outwardly of said body for some of said cutters to enlarge the diameter of the bore hole and for said cutters to operate upon a transverse formation shoulder in the bore hole.
 16. In a rotary drill bit as defined in claim 15; a first plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a first plane radial of the longitudinal axis of said body; a second plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a second plane radial of the longitudinal axis of said body; said first and second planes being arcuately displaced from each other.
 17. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members pivotally mounted at their upper portions on said body for expansion laterally outwardly of said body; each supporting member having a lower mounting base portion extending circumferentially in opposite directions substantially beyond the sides of the portion of the supporting member thereabove; a plurality of roller cutters for each supporting member; a head for each cutter; means secured to each head rotatably mounting a cutter; means for securing each head to the bottom of said base portion with its roller cutter below said base portion; said heads and cutters being so carried by said base portion that some of the cutters are circumferentially spaced from each other, some of the cutters being laterally spaced from each other; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transMitted from said mandrel to said body; coengageable expander means on said mandrel and supporting member; and means for relatively shifting said body, supporting members and roller cutters longitudinally with respect to said mandrel to cause said expander means to expand said supporting members and cutters laterally outwardly of said body for operation of said cutters upon a transverse formation shoulder in the bore hole; a first plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a first plane radial of the longitudinal axis of said body; a second plurality of said cutters carried by each supporting member being laterally spaced from each other and rotatable about axes lying in a second plane radial of the longitudinal axis of said body; said first and second planes being arcuately displaced from each other; the lateral spacing between said first plurality of cutters being substantially greater than the lateral spacing between said second plurality of cutters.
 18. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members mounted on said body for expansion laterally outwardly of said body; a plurality of roller cutters carried by each supporting member for operation upon a transverse shoulder in the bore hole; some of the cutters carried by each supporting member being circumferentially spaced from each other, some of the cutters carried by each supporting member being laterally spaced from each other; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and supporting members; said body having a cylinder portion above said expander means slidably and sealingly engaging said mandrel; said mandrel having a piston portion in said cylinder portion slidably and sealingly engaging said cylinder portion and dividing said cylinder portion into upper and lower fluid pressure chambers; and means for feeding fluid under pressure into one of said chambers to relatively shift said body, supporting members and roller cutters longitudinally with respect to said mandrel while said mandrel and body are rotated by the drill string to cause said expander means to expand said supporting members and cutters laterally outwardly of said body for some of said cutters to enlarge the diameter of the bore hole and for said cutters to operate upon the transverse formation shoulder.
 19. In a rotary drill bit as defined in claim 18; said fluid feeding means comprising a conduit externally of said mandrel communicating with said one of said chambers.
 20. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members mounted on said body for expansion laterally outwardly of said body; a plurality of roller cutters carried by each supporting member for operation upon a transverse shoulder in the bore hole; some of the cutters carried by each supporting member being circumferentially spaced from each other, some of the cutters carried by each supporting member being laterally spaced from each other; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and supporting members; said body having a cylinder portion above said expander means slidably and sealingly engaging said mandrel; said mandrel having a piston portion in said cylinder portion slidably and sealingly engaging said cylinder portion and dividing said cylinder portion into upper and lower fluid pressure chambers; and means for feeding fluid under pressure into one of said chambers to relatively shift said body, supporting members and roller cutters longitudinally with respect to said mandrel to cause said expander means to expand said supporting members and cutters laterally outwardly of said body for operation of Said cutters upon the transverse formation shoulder; a liquid confined in said other of said chambers initially preventing such relative longitudinal shifting; and means for releasing said liquid from said other of said chambers while the drill bit is in the bore hole.
 21. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members mounted on said body for expansion laterally outwardly of said body; a plurality of roller cutters carried by each supporting member for operation upon a transverse shoulder in the bore hole; some of the cutters carried by each supporting member being circumferentially spaced from each other, some of the cutters carried by each supporting member being laterally spaced from each other; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and supporting members; said body having a cylinder portion above said expander means slidably and sealingly engaging said mandrel; said mandrel having a piston portion in said cylinder portion slidably and sealingly engaging said cylinder portion and dividing said cylinder portion into upper and lower fluid pressure chambers; and means for feeding fluid under pressure into one of said chambers to relatively shift said body, supporting members and roller cutters longitudinally with respect to said mandrel to cause said expander means to expand said supporting members and cutters laterally outwardly of said body for operation of said cutters upon the transverse formation shoulder; said one of said chambers being said upper chamber whereby fluid under pressure fed thereinto elevates said body, supporting members and cutters along said mandrel.
 22. In a rotary drill bit as defined in claim 21; a liquid confined in said lower chamber initially preventing elevation of said body, supporting members and cutters along said mandrel; and means for releasing said liquid from said lower chamber while the drill bit is in the bore hole.
 23. In a rotary drill bit as defined in claim 21; a liquid confined in said lower chamber initially preventing elevation of said body, supporting members and cutters along said mandrel; and means for releasing said liquid from said lower chamber while the drill bit is in the bore hole; said fluid feeding means comprising a conduit externally of said mandrel communicating with said upper chamber.
 24. In a rotary drill bit as defined in claim 21; a liquid confined in said lower chamber initially preventing elevation of said body, supporting members and cutters along said mandrel; and means for releasing said liquid from said lower chamber while the drill bit is in the bore hole; said fluid feeding means comprising a conduit externally of said mandrel communicating with said upper chamber; and means for feeding compressed air into said mandrel to aerate the liquid column therein and in the drill string thereabove, whereby liquid in the well bore externally of the drill bit flushes cuttings into the mandrel for upward passage through the mandrel and drill string.
 25. In a rotary drill bit to be lowered in a bore hole: a main body; circumferentially spaced supporting members mounted on said body for expansion laterally outwardly of said body; a plurality of roller cutters carried by each supporting member for operation upon a transverse formation shoulder in the bore hole; some of the cutters carried by each supporting member being circumferentially spaced from each other, some of the cutters carried by each supporting member being laterally spaced from each other; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and supporting members; and means for relatively shifting said body, supporting members and roller cutters longitudinally with respect to said mandrel to cAuse said expander means to expand said supporting members and cutters laterally outwardly of said body for operation of said cutters upon the transverse formation shoulder; and means for feeding compressed air into said mandrel to aerate the liquid column therein and in the drill string thereabove, whereby liquid in the well bore externally of the drill bit flushes cuttings into the mandrel for upward passage through the mandrel and drill string.
 26. In a rotary drill bit to be lowered in a bore hole: a main body; cutter means mounted on said body for expansion laterally outwardly of said body; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and cutter means; said body having a cylinder portion above said expander means slidably and sealingly engaging said mandrel; said mandrel having a piston portion in said cylinder portion slidably and sealingly engaging said cylinder portion and dividing said cylinder portion into upper and lower fluid pressure chambers; means for feeding fluid under pressure into one of said chambers to relatively shift said body and cutter means longitudinally with respect to said mandrel to cause said expander means to expand said cutter means laterally outwardly of said body; a liquid confined in said other of said chambers initially preventing such relative longitudinal shifting; and means for releasing said liquid from said other of said chambers while the drill bit is in the bore hole.
 27. In a rotary drill bit as defined in claim 26; said one of said chambers being said upper chamber, whereby fluid under pressure fed thereinto elevates said body and cutter means along said mandrel; said other of said chamber being said lower chamber in which the liquid is confined.
 28. In a rotary drill bit as defined in claim 26; said one of said chambers being said upper chamber, whereby fluid under pressure fed thereinto elevates said body and cutter means along said mandrel; said other of said chamber being said lower chamber in which the liquid is confined; said fluid feeding means comprising a conduit externally of said mandrel communicating with said upper chamber.
 29. In a rotary drill bit as defined in claim 26; said one of said chambers being said upper chamber, whereby fluid under pressure fed thereinto elevates said body and cutter means along said mandrel; said other of said chamber being said lower chamber in which the liquid is confined; said fluid feeding means comprising a conduit externally of said mandrel communicating with said upper chamber; and means for feeding compressed air into said mandrel to aerate the liquid column therein and in the drill string thereabove, whereby liquid in the well bore externally of the drill bit flushes cuttings into the mandrel for upward passage through the mandrel and drill string. 